Peek preview for external link embeds (#10704)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/Post/Embed/ExternalEmbed/index.tsx

@@ -88,6 +88,8 @@ export const ExternalEmbed = ({
       label={link.title || _(msg`Open link to ${niceUrl}`)}
       to={link.uri}
       shouldProxy={true}
+      peek
+      style={[a.rounded_md]}
       onPress={onPress}
       onLongPress={onShareExternal}>
       {({hovered}) => (
@@ -99,6 +101,7 @@ export const ExternalEmbed = ({
             a.overflow_hidden,
             a.w_full,
             a.border,
+            t.atoms.bg,
             style,
             hovered
               ? t.atoms.border_contrast_high